Process for preparation of formate esters or methanol and catalyst therefor

ABSTRACT

A production process and a catalyst are provided, which can be less decreased in activity of the catalyst even when CO 2 , water and the like are present in the starting material and/or the reaction system, and which can produce a formic ester or a methanol at a low temperature and a low pressure.  
     The present invention relates to a process for producing methanol, comprising reacting carbon monoxide with an alcohol in the presence of an alkali metal-type catalyst, and/or an alkaline earth metal-type catalyst to produce a formic ester, wherein a hydrogenolysis catalyst of formic ester and hydrogen are allowed to be present together in the reaction system to hydrogenate the produced formic ester and thereby obtain a methanol.

TECHNICAL FIELD

[0001] The present invention relates to a process for producing a formicester or methanol and a synthesis catalyst therefor. More specifically,the present invention relates to a process for producing a methanol fromcarbon monoxide and hydrogen using a catalyst having high resistanceagainst decrease in the activity due to water or carbon dioxide andthereby obtaining a product with high efficiency, and also relates to acatalyst therefor.

BACKGROUND ART

[0002] Generally, in the industrial synthesis of a methanol, carbonmonoxide and hydrogen (synthesis gas) obtained by steam reforming of anatural gas mainly comprising methane are used as the starting materialsand the synthesis is performed using a copper/zinc-type catalyst or thelike by a fixed-bed gas phase method under severe conditions of 200-300°C. and 5-25 MPa. Although this reaction is an exothermic reaction,efficient heat extraction can be hardly attained because of poor thermalconductivity in the gas phase method and a process of lowering theone-pass conversion and recycling unreacted high-pressure startingmaterial gas is employed, which has, however, a severe problem in theefficiency. Despite such a problem, the fixed-bed gas phase method isnot easily prone to the reaction inhibition by water or carbon dioxidecontained in the synthesis gas and various plants are now operated bymaking use of this advantageous property.

[0003] On the other hand, various methods of synthesizing methanol in aliquid phase and thereby increasing the heat extraction rate are beingstudied. Among these, a method using a catalyst having high activity atlow temperatures (approximately from 100 to 180° C.) is advantageous tothe production system also in view of thermodynamics and being takennotice of. However, this method has been reported to suffer from quickdecrease in the activity due to water and carbon dioxide contained inmany cases in the synthesis gas and not used in practice.

DISCLOSURE OF INVENTION

[0004] The object of the present invention is to overcome theabove-described problems and provide a catalyst and a method, where thecatalyst activity is kept even when carbon dioxide, water and the likeare included in the starting material gas and/or the reaction system atthe synthesis of formic ester or methanol and the formic ester ormethanol can be synthesized at low temperatures and low pressures.

[0005] The present invention is characterized by the followings.

[0006] (1) A process for producing a formic ester, comprising reactingcarbon monoxide with an alcohol to produce a formic ester, wherein thereaction is performed in the presence of an alkali metal-type catalystand/or an alkaline earth metal-type catalyst.

[0007] (2) A process for producing a methanol, comprising reactingcarbon monoxide with an alcohol in the presence of an alkali metal-typecatalyst and/or an alkaline earth metal-type catalyst to produce aformic ester, wherein a hydrogenolysis catalyst of formic ester andhydrogen are allowed to be present together in the reaction system tohydrogenate the produced formic ester and thereby obtain a methanol.

[0008] (3) A process for producing a methanol, comprising reactingcarbon monoxide with an alcohol in the presence of an alkali metal-typecatalyst and/or an alkaline earth metal-type catalyst to produce aformic ester, separating the produced formic ester and hydrogenating theseparated formic ester by allowing a hydrogenolysis catalyst andhydrogen to be present together, thereby obtaining a methanol.

[0009] (4) A process for producing a methanol, comprising reacting analcohol in the presence of an alkali metal-type catalyst and/or analkaline earth metal-type catalyst, and a catalyst that includes Cusimultaneously with Mn and/or Re to obtain a methanol from carbonmonoxide and hydrogen.

[0010] (5) A process for producing a formic ester, comprising reactingcarbon monoxide with an alcohol, wherein the reaction is performed inthe presence of a catalyst containing Cu simultaneously with Mn and/orRe.

[0011] (6) The production process as described in any one of (1) to (4),wherein the alkali metal-type catalyst and the alkaline earth metal-typecatalyst include an alkali metal salt and a catalyst containing analkaline earth metal salt, respectively.

[0012] (7) The process for producing a methanol as described in (2) or(3), wherein the hydrogenolysis catalyst is a solid and the alkalimetal-type catalyst and/or the alkaline earth metal-type catalyst issupported on this solid catalyst and used for the reaction.

[0013] (8) The production process as described in any one of (1) to (5),wherein the alcohol is a primary alcohol.

[0014] (9) A catalyst for producing a methanol, which is obtained byloading an alkali metal-type catalyst and/or an alkaline earthmetal-type catalyst on a solid hydrogenolysis catalyst for formic ester.

[0015] (10) A catalyst for producing a methanol, which is composed of analkali metal-type catalyst and/or an alkaline earth metal-type catalyst,as well as a catalyst containing Cu simultaneously with Mn and/or Re.

[0016] (11) A catalyst for producing a formic ester, comprising Cusimultaneously with Mn and/or Re.

[0017] The present invention is described in detail below.

[0018] As a result of extensive investigations, the inventors of thepresent invention have found that when an alkali metal-type catalystand/or an alkaline earth metal-type catalyst substantially free frompoisoning with water and/or carbon dioxide is used, a formic ester canbe produced from a carbon monoxide and an alcohol even if water and/orcarbon dioxide co-exist. The present invention has been accomplishedbased on this finding. Examples of alkali metal-type catalysts includemetal compounds and elementary substances, such as lithium, potassium,sodium and cesium. Examples of the alkaline earth metal-type catalystsinclude metal compounds and elementary substances, such as calcium,magnesium, barium and strontium. The metal compounds are preferablymetal salts or metal oxides, more preferably alkali metal salts such ascarbonates, nitrates, phosphates, acetates and formates. Here, alkalimetal alkoxides (e.g., methoxide, ethoxide) are excluded because theseare substantially subjected to poisoning with water and/or carbondioxide. Those catalysts can also be used as a catalyst supported on ageneral support by an ordinary method. The alcohols used for thereaction are an alcohol resultant from bonding of a hydroxyl group to achained or alicyclic hydrocarbon and in addition, may be a phenol or asubstitution product thereof, or a thiol or a substitution productthereof. These alcohols may be primary, secondary or tertiary alcohols,but preferably primary alcohols due to their reaction efficiency. Loweralcohols, such as methyl alcohol or ethyl alcohol, are most commonlyused. The reaction may be performed in either the liquid or gas phasebut a system where moderate conditions can be selected may be employed.To speak specifically, the temperature, the pressure and the reactiontime are selected from 70 to 250° C., 3 to 70 atm and 5 minutes to 10hours, respectively, however, the conditions are not limited thereto.The alcohol may be sufficient if the amount added thereof issufficiently large to allow the reaction to proceed, however, thealcohol may also be used as a solvent and in an amount larger than that.In this reaction, organic solvents other than alcohols may beappropriately used in combination.

[0019] A catalyst containing Cu simultaneously with Mn and/or Re mayalso be used in the production of a formic ester.

[0020] The obtained formic ester may be purified by an ordinary methodbut may also be used as it is in the production of a methanol. That is,a methanol can be produced by hydrogenating the formic ester. For thehydrogenolysis, a hydrogenolysis catalyst is used and examples of thecatalyst which can be used include general hydrogenolysis catalystscontaining Cu, Pt, Ni, Co, Ru or Pd. More specifically, copper-typecatalysts such as Cu/MnO_(X), Cu/ReO_(X) (wherein X is a chemicallyallowable value), Cu/ZnO, Cu/CrO₃ and Raney copper, and nickel-typecatalysts are suitably used. Among these, Cu/MnO_(X) and Cu/ReO_(x)exhibit extremely high activities in this reaction and ensure a highmethanol yield even when water and/or carbon dioxide are present. Themethod for preparing the hydrogenolysis catalysts is not particularlylimited and an ordinary method may be used, such as impregnation method,precipitation method, sol-gel method, coprecipitation method, ionexchange method, kneading method and drying method. However, accordingto the coprecipitation method, a catalyst having a high loading amountcan be prepared and good results can be readily obtained. In the presentinvention, this hydrogenolysis catalyst and hydrogen are allowed to bepresent together in the reaction system for producing a formic esterfrom a carbon monoxide and an alcohol, whereby a methanol can beproduced by a so-called one-step process. The hydrogenolysis reactioncan be performed fundamentally under the above-described reactionconditions, however, the temperature and the pressure may beappropriately changed. The hydrogen/carbon monoxide ratio is generallyselected in the range approximately from 1 to 5. As described above, inthe case of performing the reaction while allowing a hydrogenolysiscatalyst to be present together with an alkali metal-type catalyst andthe like, these catalysts may be used as a simple mixture, however, whenthe alkali metal-type catalyst is supported on the solid hydrogenolysiscatalyst, the recovery of the catalysts is advantageously facilitated.With respect to the loading method itself, an ordinary method employedin the preparation of catalysts may be used.

[0021] In the case where a methanol can hardly be produced by theone-step process, it is also possible to obtain a methanol by separatingthe produced formic ester and then hydrogenolyzing the separated formicester in the presence of a hydrogenolysis catalyst and hydrogen.

[0022] The process for producing a formic ester or a methanol accordingto the present invention is presumed to proceed according to thefollowing reaction scheme (as an example, a case of using an alcoholresulting from bonding a hydroxyl group to a chained or alicyclichydrocarbon is shown):

R—OH+CO→HCOOR  (1)

HCOOR+2H₂→CH₃OH+R—OH  (2)

[0023] (wherein R represents an alkyl group).

[0024] As such, carbon monoxide and hydrogen are used as the startingmaterials for producing a methanol and the alcohol can be recovered andreused. According to the present invention, even where a fairly largeamount of water and carbon dioxide are present in the starting materialgas (for example, even with at least 5% of carbon dioxide) and/or thereaction system, the catalyst does not lose its activity and a formicester or a methanol can be produced. Furthermore, even where asulfur-type compound and a chlorine-type compound, such as H₂S and HCl,are mingled in the reaction system, the formic ester or a methanol canbe similarly produced without any problem.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The present invention is described in greater detail by referringto the Examples given below, although the present invention is notlimited to these Examples.

[0026] In the Examples, the CO conversion and the methanol yield werecalculated according to the following formulae:

CO conversion (%)=[1−(molar number of CO+CO₂ recovered afterreaction)/(molar number of CO+CO₂ charged)]×100

Methanol yield (%)=((molar number of methanol produced)/(molar number ofCO+CO₂ charged))×100

EXAMPLE 1

[0027] In an autoclave having a content volume of 80 ml, 0.72 mmol ofpotassium carbonate was added to 10 ml of ethanol containing 1% by massof water as a solvent, a carbon dioxide mixed synthesis gas (CO: 32%,CO₁: 4.7%, balance: hydrogen) was filled to 3 MPa, and the reaction wasperformed at 170° C. for 2 hours. The reaction product was analyzed bygas chromatograph, as a result, it was found that only ethyl formate wasobtained with a CO conversion of 3.0%.

EXAMPLE 2

[0028] The reaction was performed by the method described in Example 1except for changing the reaction time to 20 minutes. The same results asin Example 1 were obtained and it was revealed that the reaction reachedthe equilibrium in 20 minutes.

EXAMPLE 3

[0029] The reaction was performed by the method described in Example 1except for adding potassium hydrogencarbonate in place of potassiumcarbonate. As a result, ethyl formate was obtained with a Co conversionof 3.1%.

EXAMPLE 4

[0030] The reaction was performed by the method described in Example 1except for adding cesium carbonate in place of potassium carbonate. TheCO conversion was 3.2%.

EXAMPLE 5

[0031] The reaction was performed by the method described in Example 1except for adding sodium carbonate in place of potassium carbonate. TheCO conversion was 1.36%.

EXAMPLE 6

[0032] The reaction was performed by the method described in Example 1except for adding lithium carbonate in place of potassium carbonate. TheCo conversion was 0.4%.

EXAMPLE 7

[0033] The reaction was performed by the method described in Example 1except for adding potassium nitrate in place of potassium carbonate. TheCO conversion was 1.0%.

EXAMPLE 8

[0034] The reaction was performed by the method described in Example 1except for adding sodium nitrate in place of potassium carbonate. The COconversion was 0.9%.

EXAMPLE 9

[0035] The reaction was performed by the method described in Example 1except for adding potassium phosphate in place of potassium carbonate.The CO conversion was 1.7%.

EXAMPLE 10

[0036] The reaction was performed by the method described in Example 1except for adding potassium acetate in place of potassium carbonate. TheCO conversion was 1.51%.

EXAMPLE 11:

[0037] The reaction was performed by the method described in Example 1except for adding potassium formate in place of potassium carbonate. TheCO conversion was 3.44%.

EXAMPLE 12

[0038] The reaction was performed by the method described in Example 1except for using methanol in place of ethanol, as a result, the COconversion was 4.0% (methyl formate).

EXAMPLE 13

[0039] The reaction was performed by the method described in Example 1except for using n-propanol in place of ethanol. The CO conversion was3.4% (n-propyl formate).

EXAMPLE 14

[0040] The reaction was performed by the method described in Example 1except for using n-butanol in place of ethanol. The CO conversion was3.4% (n-butyl formate).

EXAMPLE 15

[0041] The reaction was performed by the method described in Example 1except for using i-propanol in place of ethanol. The CO conversion was1.1% (i-propyl formate).

EXAMPLE 16

[0042] The reaction was performed by the method described in Example 1except for using i-butanol in place of ethanol. The CO conversion was1.8% (i-butyl formate).

EXAMPLE 17

[0043] The reaction was performed by the method described in Example 1except for using t-butanol in place of ethanol. The CO conversion was0.7% (t-butyl formate).

EXAMPLE 18

[0044] The reaction was performed by the method described in Example 1except for further adding 0.2 g of a copper/zinc coprecipitated catalystas the hydrogenolysis catalyst. As a result, methanol was obtained withthe CO conversion of 2.9% and the methanol yield of 0.3%.

EXAMPLE 19

[0045] In an autoclave having a content volume of 85 ml, 1.4 mmol ofpotassium carbonate was added to 20 ml of ethanol containing 0.010% bymass of water as a solvent, a carbon dioxide mixed synthesis gas (CO:32%, CO₂: 4.7%, balance: hydrogen) was filled to 3.0 MPa, and thereaction was performed at 170° C. for 2 hours. The reaction product wasanalyzed by gas chromatograph. As a result, it was found that only ethylformate was obtained with the Co conversion of 16%.

EXAMPLE 20

[0046] The reaction was performed by the method described in Example 19except for further adding 4.0 g of a copper/zinc coprecipitated catalystas the hydrogenolysis catalyst. As a result, methanol was obtained withthe CO conversion of 25% and the methanol yield of 1.2%.

EXAMPLE 21

[0047] The reaction was performed by the method described in Example 19except for further adding 4.0 g of a copper/manganese coprecipitatedcatalyst as the hydrogenolysis catalyst. As a result, methanol wasobtained with the CO conversion of 90% and the methanol yield of 27%.

EXAMPLE 22

[0048] The reaction was performed by the method described in Example 19except for further adding 2.0 g of a copper/manganese coprecipitatedcatalyst as the hydrogenolysis catalyst. As a result, methanol wasobtained with the CO conversion of 79% and the methanol yield of 27%.

EXAMPLE 23

[0049] The reaction was performed by the method described in Example 19except for further adding 1.0 g of a copper/manganese coprecipitatedcatalyst as the hydrogenolysis catalyst. As a result, methanol wasobtained with the CO conversion of 33% and the methanol yield of 1.1%.

EXAMPLE 24

[0050] The reaction was performed by the method described in Example 22except that the mixed synthesis gas did not contain CO₂. As a result,methanol was obtained with the CO conversion of 92% and the methanolyield of 41%.

1. A process for producing a formic ester, comprising reacting carbonmonoxide with an alcohol to produce a formic ester, wherein the reactionis performed in the presence of an alkali metal-type catalyst and/or analkaline earth metal-type catalyst.
 2. A process for producing amethanol, comprising reacting carbon monoxide with an alcohol in thepresence of an alkali metal-type catalyst and/or an alkaline earthmetal-type catalyst to produce a formic ester, wherein a hydrogenolysiscatalyst for formic ester and hydrogen are allowed to be presenttogether in the reaction system to hydrogenate the produced formic esterand thereby obtain a methanol.
 3. A process for producing a methanol,comprising reacting carbon monoxide with an alcohol in the presence ofan alkali metal-type catalyst and/or an alkaline earth metal-typecatalyst to produce a formic ester, separating the produced formic esterand hydrogenating the separated formic ester by allowing ahydrogenolysis catalyst and hydrogen to be present together, therebyobtaining a methanol.
 4. A process for producing a methanol, comprisingreacting an alcohol in the presence of an alkali metal-type catalystand/or an alkaline earth metal-type catalyst, and a catalyst containingCu simultaneously with Mn and/or Re to obtain a methanol from carbonmonoxide and hydrogen.
 5. A process for producing a formic ester,comprising reacting carbon monoxide with an alcohol, wherein thereaction is performed in the presence of a catalyst containing Cusimultaneously with Mn and/or Re.
 6. The production process as claimedin any one of claims 1 through 4, wherein the alkali metal-type catalystand the alkaline earth metal-type catalyst are a catalyst containing analkali metal salt and a catalyst containing an alkaline earth metalsalt, respectively.
 7. The process for producing a methanol as claimedin claim 2 or 3, wherein the hydrogenolysis catalyst is a solid catalystand the alkali metal-type catalyst and/or the alkaline earth metal-typecatalyst is supported on said solid catalyst and used for the reaction.8. The production process as claimed in any one of claims 1 through 5,wherein the alcohol is a primary alcohol.
 9. A catalyst for producing amethanol, which is obtained by loading an alkali metal-type catalystand/or an alkaline earth metal-type catalyst on a solid hydrogenolysiscatalyst for formic ester.
 10. A catalyst for producing a methanol,which is composed of an alkali metal-type catalyst and/or an alkalineearth metal-type catalyst, and a catalyst containing Cu simultaneouslywith Mn and/or Re.
 11. A catalyst for producing a formic ester,comprising Cu simultaneously with m and/or Re.